booblik-client

Generated page

Model gemma-mtp, commit ef58254ca7be, 2026-08-16, sources: 6. Edit the code or the hand-written documentation instead.

The low-level, blocking, single-socket client for sending raw requests. It provides the most basic interface for sending PRODUCE, FETCH, and METADATA requests directly to a SocketChannel BooblikClient.kt:24-88.

More: BooblikClient

BooblikConnection

The pipelined connection mechanism that manages concurrent requests via a single writer coroutine and a FIFO response queue. It uses an AtomicInteger to manage correlationIds BooblikConnection.kt:71 and ensures that responses are matched to callers in strict order, failing loudly if the broker reorders them BooblikConnection.kt:34-38.

More: BooblikConnection

Producer

The high-level accumulator that batches records by partition and manages the lingerMillis and maxBatchSize logic Producer.kt:21-34. It uses a mailbox to receive Command.Append requests and an internal runLoop to decide when to trigger a deliver call based on the configured ProducerConfig Producer.kt:54-173.

More: Producer

Consumer

The stateful reader that manages the position offset and handles RecordExceedsMaxBytesException during polling Consumer.kt:56-97. It tracks the current position and advances it only past whole records when a poll is successful Consumer.kt:56-97.

ResponseReader

The decoding layer that handles frame reading and checksum verification for FETCH responses. It reads the length-prefixed frames from a SocketChannel and delegates decoding to the protocol module, specifically handling the translation of CorruptRecordException ResponseReader.kt:55-109.

ResponseEncoder

The construction of response frames, specifically the zero-copy header mechanism for FETCH responses. It distinguishes between "promised" bytes (the body to be streamed) and "inline" bytes (the header) to support efficient zero-copy reading ResponseEncoder.kt:15-117.

Key files

File	Lines	What is there
`…/client/BooblikClient.kt`	`24-88`	The low-level blocking client implementation.
`…/client/BooblikConnection.kt`	`50-241`	The pipelined connection and coroutine-based writer/reader.
`…/client/Producer.kt`	`54-264`	The batching producer implementation.
`…/client/Consumer.kt`	`56-113`	The stateful consumer implementation.
`…/client/ResponseReader.kt`	`55-118`	The response decoding and frame reading logic.
`…/wire/ResponseEncoder.kt`	`15-130`	The logic for encoding response frames and headers.

Public API

What	Where	Why
`BooblikClient`	`BooblikClient.kt:24`	Low-level client for raw requests.
`BooblikConnection`	`BooblikConnection.kt:50`	Pipelined connection for concurrent requests.
`Producer`	`Producer.kt:54`	High-level batching producer.
`ProducerConfig`	`Producer.kt:21`	Configuration for batching and ack policy.
`Consumer`	`Consumer.kt:56`	Stateful partition reader.
`ResponseReader`	`ResponseReader.kt:55`	Object for decoding response frames.
`ResponseEncoder`	`ResponseEncoder.kt:15`	Object for encoding response frames.

Behaviour that surprises

The Producer uses a select expression in its runLoop to avoid a specific bug where a cancelled receive could drop elements from the mailbox, potentially causing callers to wait forever Producer.kt:154-158.
The Consumer can throw a RecordExceedsMaxBytesException if a record is larger than the maxBytes limit, which results in a permanent stall if the reader does not increase its limit Consumer.kt:28-36.
The ResponseEncoder uses a "promised" vs "inline" byte mechanism for fetchHeader to allow the client to perform zero-copy reads of the response body ResponseEncoder.kt:39-41.